# Replacement wall charger question
**URL:** https://boards.straightdope.com/t/replacement-wall-charger-question/587225
**Category:** Factual Questions
**Created:** [June 29, 2011, 1:43am UTC](https://boards.straightdope.com/t/replacement-wall-charger-question/587225 "2011-06-29T01:43:01Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@Jayrot](https://boards.straightdope.com/u/Jayrot)
#### Post date: [June 29, 2011, 1:43am UTC](https://boards.straightdope.com/t/replacement-wall-charger-question/587225/1 "2011-06-29T01:43:01Z")
I lost the wall charger for this air pump thing that I have. I want to buy a replacement charger, but I don’t know the exact specs. I’ll probably just get a universal charger, and looking at the writing on the pump it says 4.8V, but it doesn’t tell me if the pin is + or -. There isn’t that usual diagram thingy that you see on other electronics. Is there any way to figure it out? Is one config more common than others? What happens if I put the wrong tip on?
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### Author:  [@Digital\_is\_the\_new\_Analog](https://boards.straightdope.com/u/Digital_is_the_new_Analog)
#### Post date: [June 29, 2011, 2:44am UTC](https://boards.straightdope.com/t/replacement-wall-charger-question/587225/2 "2011-06-29T02:44:34Z")
If you can find something else that you are convinced is ground, you could use a multi-meter to figure out which part of the plug is ground…
Or you could check the internet for the pump you have. The internet is \*\*really \*\*smart…
-D/a
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### Author:  [@BigT](https://boards.straightdope.com/u/BigT)
#### Post date: [June 29, 2011, 3:16am UTC](https://boards.straightdope.com/t/replacement-wall-charger-question/587225/3 "2011-06-29T03:16:18Z")
So is that open-end-plus [(-) --C-- (+)] or open-end-minus [(-) --Ↄ-- (+)]?
Heck, I’m not sure if open-end-minus is written (+) --C-- (-), since I haven’t seen it in so long. But you get what I’m asking right? Which part of the symbol refers to the ground?